FRONTIERS OF ZOOLOGY Dale A. Drinnon has been a researcher in the field of Cryptozoology for the past 30+ years and has corresponded with Bernard Heuvelmans and Ivan T. Sanderson. He has a degree in Anthropology from Indiana University and is a freelance artist and writer. Motto: "I would rather be right and entirely alone than wrong in the company with all the rest of the world"--Ambroise Pare', "the father of modern surgery", in his refutation of fake unicorn horns.
Scott Mardis just emailed me this passage from the book The Original Vermonters, pages 194-195, in hopes that it would provide some background for the monster in Lake Champlain.
The underlining in red is mine.
From this I gather that there were a few well-defined Cryptids involved and some that were rather less certain. A large lizardlike or otterlike creature is one of them, and that is the one which is thought to have made burrows that were known to sometimes drain pools. The otterlike component of this myth is better defined by this habit of digging dens, but it is also possible that a kind of a giant salamander was being called a "Water Lizard" (Giant salamanders and specifically Giant Hellbenders have been alleged at Lake Champlain a number of times, but without any strong evidence being cited) The Great Horned Water Serpent is believed in generally throughout the area, but this is one definite instance where the description is that of a swimming moose (specifically because of the horselike head) The Swamp Monsters and Little people I take to be two forms of the same thing, and reported more recently as "Giant Frogs". These are Kappalike creatures and interestingly enough these mineral formations are pointed out as being an indication of their presence. A more prosaic explanation would be that this is what their feces look like. "Submerging in their stone canoes" is simply a way of saying they submerged, the phrase "The monster sank out of sight like a stone" being familiar in other contexts.
This is very useful information but none of it clearly pertains to a Plesiosaur-shaped creature, which is unfortunate. None of it clearly refers to landlocked seals or small whales either, for that matter.